dart_pkg cleanups

mojo/dart/http_load_test/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/dart/rules.gni")
 
 dart_pkg("http_load_test") {
-  apps = [ "lib/main.dart" ]
-  app_name_override = "dart_http_load_test"
+  apps = [ [
+        "dart_http_load_test",
+        "lib/main.dart",
+      ] ]
   sources = [
     "lib/src/part0.dart",
     "pubspec.yaml",
   ]
   deps = [
     "//mojo/public/dart",
     "//mojo/dart/mojo_services",
   ]
 }